Separating blood components for transfusion or intra-operative red blood cell (“RBC”) salvage has been a standard practice of medicine for the last 50 years. These procedures generally involve relatively large volumes of blood, and in the case of blood banking are usually not for autologous use. Additionally, laboratories have been separating blood proteins for diagnostic testing for years. Improved methods for fractionating blood samples have allowed for better separation of factions.
Smaller blood separation devices have been introduced into the market for concentrating, for example, platelets from a small volume of blood. These devices allow for improved concentration of, for example, the growth factors in platelets that can be applied topically or injected locally to patients. These devices typically rely upon an apheresis method or a rigid plastic disposable device with density shelves for separating components of relatively small volumes of blood.
Increasingly, the therapeutic potential of stem cells is being recognized for many clinical applications including, for example, regenerative therapy. Certain early pioneers of stem cell technology used blood banking equipment designed for transfusion medicine or small volume platelet concentration systems to concentrate stem cells at point of care from marrow or umbilical cord blood. Both of these methods present the practitioner with varying problems such as the large volume of marrow aspirate required, varying volumes of umbilical blood processed, and low percent yields in the ending concentrate.
Stem cells are found in specific blood samples, two rich sources of stem cells being umbilical cord blood and bone marrow. During fractionation by sedimentation, stem cells in these samples typically migrate in a small volume known as the “buffy coat” fraction. The buffy coat fraction appears as a small volume density layer after sedimentation. Because mononuclear cells and stem cells present in the buffy coat represent such a small percentage of the overall volume of cord blood and marrow, and because clinical applications using stem cells require highly concentrated buffy coat fractions, there is a well-demonstrated and increasing need to capture and concentrate a high percentage of these cells into a small volume.